1. Field of the Invention
The present invention relates to an inspecting method and an apparatus for a foreign matter for detecting a foreign matter(impurities) got entered a liquid product(including a fluid product), such as drinks and liquid drugs, and more particularly to inspecting method and apparatus for a foreign matter capable of detecting, at high speed and accuracy, a foreign matter got entered a liquid product inside a container of such a complicated shape that makes inspection difficult by improving a light irradiating optical system used for inspection.
2. Description of the Related Background Art
Adoption of the HACCP (Hazard Analysis Critical Control Point) system to the Food Sanitation Law and enforcement of the PL(Product Liability) Law in recent years have been making it mandatory to further ensure the product safety by forestalling a hazard, such as microbial contamination and entrance of foreign matters like metal, fabrics, hair, etc., that could occur in any stage from manufacturing/processing of products, such as food and drugs, to consumption by end consumers through storage/distribution of the products.
HACCP is a hazard analysis and critical control point system established in the United States and is highly evaluated across the world as a sanitary control system method. The HACCP system is a science-based sanitary control system in which product safety is addressed throughout the manufacturing procedure so that preventive measures in the manufacturing procedure are emphasized in contrast to a conventional sanitary control system in which inspection of final products is emphasized. The HACCP system includes two sections: hazard analysis(HA) and critical control point(CCP), and it further ensures the product safety by forestalling an occurrence of a hazard in the manufacturing procedure without overlooking any possibility by (1) checking/analyzing a hazard, such as microbial contamination, that could occur in any stage from manufacturing/processing of food to consumption by end consumers through storage/distribution of the products and setting critical control points to prevent the hazard, (2) setting the criteria of control and constantly monitoring whether the critical limit is being met by checking the records of control, and (3) managing and controlling hazards of other natures with a pre-requisite program(PP).
In a conventional mass-production line of a manufacturing factory, workers detect foreign matters got entered liquids filled in containers by visual inspection. Because such visual inspection is tedious and time-consuming, it is conducted on spot-check basis that one in every certain number of containers is picked up and inspected. Hence, there is a problem that it is by no means reliable inspection conducted for each individual product.
In the case of a method on one hundred percent inspection basis by deploying inspectors along the production line, the inspectors(workers) are able to detect relatively large foreign matters by visual inspection, but they fail in detecting minute foreign matters, which raises a problem that the detection is less accurate. More importantly, the ability of visual inspection of the inspectors is no longer comparable to an increasing speed of the production line, and it is true that the inspection efficiency is becoming poor.
As a method for detecting a foreign matter got entered a container filled with a liquid other than the visual inspection, the container may be pictured from the outside by an inspection camera, so that the presence or absence of non-conformity is detected based on the resulting image information.
FIG. 1 is a view showing an example of such a method. According to this method, a light source 100 irradiates a PET bottle 101, namely an object being inspected, from the side face thereof, and transmitted light from the PET bottle 101 is received by a CCD sensor 102 serving as an imaging means. Then, a light reception signal from the CCD sensor 102 is subjected to image processing by a data processing apparatus (not shown), whereby a foreign matter got entered a liquid product inside the PET bottle 101 is detected.
With the inspecting apparatus arranged as above, the CCD sensor 102 receives transmitted light from the PET bottle 101, and the image processing apparatus, such as a personal computer, processes the light reception signal from the CCD sensor 102, so that a foreign matter got entered the liquid product inside the PET bottle 101 is detected. In this case, there is considerable interference on the surface of the container, such as reflection of scattered light from the outside and a bright line, which is resulted from a complicated shape of the container or the materials of the container, and irregularities on the surface of the container and the contour line of the container cause a change in intensity in the same way as a foreign matter does. For this reason, an image information(raw data) as shown in FIG. 2 is obtained at the CCD sensor 102. Therefore, even if the image processing apparatus processes the image information and converts the same into a binary image as shown in FIG. 3, it is difficult to precisely identify a foreign matter alone on the image thus obtained. In other words, besides a problem that the reliability is lowered, there is a problem that irregular reflection on the container is erroneously detected as a foreign matter and manufacturing yield is reduced.
There is known another detecting method, according to which a foreign matter is detected by inducing motions in a liquid by rotating a container filled with the liquid, and by obtaining the trail of associated movements of a foreign matter as the image information. This method, however, is feasible on the precondition that the container is of a simple shape having no irregularities on the surface, and therefore, it has a drawback that containers subjected to inspection are limited. Also, because an inspection time per container is too long, this method has a problem that it is not suitable for use in a high-speed mass-production line for drinks or liquid drugs.
Further, a method of masking a portion that need not be inspected, such as a mold line of the container, by editing a pictured image with software may be proposed. However, the products are generally flown into an imaging area of the inspecting apparatus provided to the production line at various rotational angles. Hence, when the containers are pictured as images, the position of the irregularities on the surface of the container varies from image to image, which poses a problem that it is virtually impossible to set a fixed masking area.
Additionally, the conventional inspecting apparatus is not able to detect a foreign matter by an optical method or irradiation of laser beams when a colored translucent PET bottle or bottle is filled with a transparent liquid, or when a transparent PET bottle or bottle is filled with a colored liquid, such as coffee, juice or cola. A foreign matter may be detected with X-rays when the container is opaque or translucent. However, the X-rays per se have ill effects on the human body; moreover, a large-scale and fairly expensive apparatus needs to be installed.
For this reason, the inspection of a bottle or a PET bottle for a foreign matter has not been conducted at all once a colored liquid product is filled therein. However, in order to attain the perfection of the products, there has been a need to conduct the inspection of bottles or PET bottles for foreign matters in a reliable manner whether the liquids are transparent or colored.